Virtual destructors should have virtual keyword.

chrome/browser/printing/print_dialog_gtk.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_PRINTING_PRINT_DIALOG_GTK_H_
 #define CHROME_BROWSER_PRINTING_PRINT_DIALOG_GTK_H_
 #pragma once
 
 #include <gtk/gtk.h>
 #include <gtk/gtkprintunixdialog.h>
@@ skipping 35 matching lines @@
   virtual void PrintDocument(const printing::Metafile* metafile,
                              const string16& document_name);
   virtual void AddRefToDialog();
   virtual void ReleaseDialog();
 
  private:
   friend struct BrowserThread::DeleteOnThread<BrowserThread::UI>;
   friend class DeleteTask<PrintDialogGtk>;
 
   explicit PrintDialogGtk(PrintingContextCairo* context);
-  ~PrintDialogGtk();
+  virtual ~PrintDialogGtk();
 
   // Handles dialog response.
   CHROMEGTK_CALLBACK_1(PrintDialogGtk, void, OnResponse, int);
 
   // Saves data in |metafile| to disk for document named |document_name|.
   void SaveDocumentToDisk(const printing::Metafile* metafile,
                           const string16& document_name);
 
   // Prints document named |document_name|.
   void SendDocumentToPrinter(const string16& document_name);
@@ skipping 21 matching lines @@
 
   // Event to signal when save document finishes.
   scoped_ptr<base::WaitableEvent> save_document_event_;
 
   FilePath path_to_pdf_;
 
   DISALLOW_COPY_AND_ASSIGN(PrintDialogGtk);
 };
 
 #endif  // CHROME_BROWSER_PRINTING_PRINT_DIALOG_GTK_H_